Superflow decay in a toroidal Bose gas: The effect of quantum and thermal fluctuations

We theoretically investigate the stochastic decay of persistent currents in a toroidal ultra cold atomic superfluid caused by a perturbing barrier. Specifically, we perform detailed three-dimensional simulations to model the experiment of Kumar et al. in [Phys. Rev. A 95 021602 (2017)], which observed a strong temperature dependence in the timescale of superflow decay in an ultracold Bose gas. Our ab initio numerical approach exploits a classical-field framework that includes thermal fluctuations due to interactions between the superfluid and a thermal cloud, as well as the intrinsic quantum fluctuations of the Bose gas. In the low-temperature regime our simulations provide a quantitative description of the experimental decay timescales, improving on previous numerical and analytical approaches. At higher temperatures, our simulations give decay timescales that range over the same orders of magnitude observed in the experiment, however, there are some quantitative discrepancies that are not captured by any of the mechanisms we explore. Our results suggest a need for further experimental and theoretical studies into superflow stability.

Automated summary

This theoretical investigation focuses on the stochastic decay of persistent currents in a toroidal ultra cold atomic superfluid, caused by a perturbing barrier. The study utilizes detailed three-dimensional simulations to model an experiment, observing a strong temperature dependence in the timescale of superflow decay. Results of the simulations show quantitative discrepancies at higher temperatures, suggesting the need for further experimental and theoretical studies on superflow stability.